1. Technical Field
The present invention relates to memory access control and, more particularly, to circuitry for determining memory client priority access to memory.
2. Related Art
With increase density, today's electronic circuits are becoming increasingly complex supporting development of entire systems on a single chip or at least in a small package. Moreover, such advances allow devices to be developed for sale at a low cost that include increasingly greater functionality. As such, many protocol systems and devices may be collocated wherein such devices share some hardware such as memory. In today's environment, however, where many different systems may seek access in real time to a common resource such as memory, memory control becomes an increasingly important part of creating a device or system that has substantial functionality. Because much of this functionality has real time memory access requirements that cause the functionality to fail or degrade if memory latency is too high (for example if required access times are exceeded), a memory control system that can service the memory access requests from the various functional modules.
Mobile devices, with such substantial functionality, now allow users to effectively have powerful computing devices that support a vast array of popular functionality for data delivery, communication services of many types, etc. One aspect of such mobile devices, however, is that power savings modes are required to extend battery life to enable the user to go longer periods without having to recharge or replace batteries. Thus, power modes of operation are often designed into systems to reduce power consumption by the various modules within a device according to operational modes and operational requirements. In many cases, a circuit may be powered down to either an off state or a reduced power state for a fraction of a second. Cumulatively, such power cycles serve to reduce power consumption and to increase battery life.
Communication systems are known to support wireless and wire lined communications between wireless and/or wire lined communication devices. Such communication systems range from national and/or international cellular telephone systems to the Internet to point-to-point in-home wireless networks. Each type of communication system is constructed, and hence operates, in accordance with one or more communication standards. For instance, wireless communication systems may operate in accordance with one or more standards, including, but not limited to, IEEE 802.11, Bluetooth, advanced mobile phone services (AMPS), digital AMPS, global system for mobile communications (GSM), code division multiple access (CDMA), local multi-point distribution systems (LMDS), multi-channel-multi-point distribution systems (MMDS), and/or variations thereof.
Depending on the type of wireless communication system, a wireless communication device, such as a cellular telephone, two-way radio, personal digital assistant (PDA), personal computer (PC), laptop computer, home entertainment equipment, etc., communicates directly or indirectly with other wireless communication devices. For direct communications (also known as point-to-point communications), the participating wireless communication devices tune their receivers and transmitters to the same channel or channels (e.g., one of a plurality of radio frequency (RF) carriers of the wireless communication system) and communicate over that channel(s). For indirect wireless communications, each wireless communication device communicates directly with an associated base station (e.g., for cellular services) and/or an associated access point (e.g., for an in-home or in-building wireless network) via an assigned channel. To complete a communication connection between the wireless communication devices, the associated base stations and/or associated access points communicate with each other directly, via a system controller, via a public switch telephone network (PSTN), via the Internet, and/or via some other wide area network.
Each wireless communication device includes a built-in radio transceiver (i.e., receiver and transmitter) or is coupled to an associated radio transceiver (e.g., a station for in-home and/or in-building wireless communication networks, RF modem, etc.). As is known, the transmitter includes a data modulation stage, one or more intermediate frequency stages, and a power amplifier stage. The data modulation stage converts raw data into baseband signals in accordance with the particular wireless communication standard. The one or more intermediate frequency stages mix the baseband signals with one or more local oscillations to produce RF signals. The power amplifier stage amplifies the RF signals prior to transmission via an antenna.
Typically, the data modulation stage is implemented on a baseband processor chip, while the intermediate frequency (IF) stages and power amplifier stage are implemented on a separate radio processor chip. Historically, radio integrated circuits have been designed using bi-polar circuitry, allowing for large signal swings and linear transmitter component behavior. Therefore, many legacy baseband processors employ analog interfaces that communicate analog signals to and from the radio processor.
In a mobile wireless device, therefore, many such communication systems may be included in addition to systems or modules that perform other functionality. Many such modules have frequent necessity to access memory to retrieve data, to store data, or to refresh or update a user interface device such as a display or a speaker. Accordingly, power savings modes of operation may depend not only upon whether a device or module is currently being used and is in an operational mode, but also upon known timing characteristics of a particular operation of the module or system. For example, according to an associated communication protocol supported by a particular module, a power saving mode of operation may be able to determine that a circuit may be powered down and powered back up within a period before the module is required to operate.